Electromagnetic relay with spring loaded armature



H. s'AuER July 21, 1959 ELECTROMAGNETIC RELAY WITH SPRING LOADED ARMATURE Filed Mai-oh 7. 1955 INVENTOR. H a na 3 ans r United States Patent p" ELECTROMAGNETIC RELAY WITH SPRING LOADED ARMATURE Hans Sauer, Chicago, Ill., assignor to Comar Electric Company, Chicago, 111., a corporation of Illinois Application March 7, 1955, Serial No. 492,451

8 Claims. (Cl. 317-199) This invention pertains to electromagnetic relays and the like and has as its principal object the provision of novel self-adjusting spring means for relay armatures in accordance with which the characteristic of the spring force automatically conforms itself to a predetermined desired pattern as a function of the travel of displacement of the armature. It is a further object to provide a sensitive manual adjustment for modifying the springaction pattern.

The magnetic pull on a relay armature during the entire range of travel thereof must normally be stronger than the effective force of whatever spring means is employed to maintain the armature in its intended normal, neutral, or non-operated position. By reason of the fact that the magnetic pull acts according to the square law and increases approximately as a square function as the air gap narrows down, the pull in the neutral position of the armature is small compared to the counteraction of the usual spring means commonly employed to normalize armatures, while at the end of the armature travel this pull becomes stronger than the force of the spring in those cases, for example, where the characteristic of the spring follows a linear function. In such a case the pull-in is comparatively high.

This pull-in is decreased substantially when the characteristic of the armature spring is made to conform to the character of the magnetic pull acting on the armature.

It is an object of this invention to change the spring constant conformably to the displacement of the armature from its starting or neutral position, for example, by provision of means including a spring which shortens its effective length to conform to the magnetic-forcedisplacement curve required.

An automatic shortening of the effective length of the spring during the armature travel can be realized by a spring bent with an arcuate curvature rolling off from a surface associated with the armature and having an end bearing upon a surface which is stationary relative to the armature.

Additional objects and aspects of novelty and utility inherent in the invention will appear as the following description proceeds in view of the annexed drawing, in which:

Fig. 1 is a schematic depiction of the invention applied to a polarized relay; and

Fig. 1a is a graphical representation of the resultant spring action achieved by constructions according to the invention.

Referring to Fig. l, the opposite ends of the core K for coil W are provided with heel pieces J and J having pole pieces Q and Q the latter being set between the pole shoes A A of a permanent-magnet armature A mounted by suitable bearing means for pivotal movement about an axis a normal to the drawing plane. The direction of magnetization of the permanently-magnetized armature member A is shown by the arrows on the latter. The pole shoe A carries a flat 2,896,132 Patented July 21, 1959 piece A on opposite sides of which are positioned springs F and F respectively fastened at one end at said pole shoe A These springs are curved in a suitable manner, for example, circularly in opposite directions and set with their ends bearing on stationary counterbearings G and G In order to adjust the armature easily and exactly in the neutral position shown with a certain spring tension, it is desirable to make the counterbearings sensitively adjustable as shown in Fig. l for the counterbearing G This counterbearing may be made by a rectangularly bent loop of spring band material. One end of the spring band contacts diagonally the other end and can be adjusted, more or less downwardly, by a set screw st which penetrates the loop. By this action the end of the spring loop which engages the spring F extends toward the latter and influences more or less the tension of this spring F Similar adjustment can be had for the counterbearing G The springs F and F are fastened at the piece A at their lower ends only, and are curved in such manner that they stand away arcuately from their points of attachment if there is no applied counter-tension. As shown in the illustrative example, the springs F and F are sprung by the counterbearings G G so much that their lower end portions contact the surfaces of the member A along the length of the latter as far as the point x. In this neutral position the resultant force of both springs upon the armature is equal to zero.

By operating the relay on direct current in such manner that a north pole is generated in the pole piece Q and a south pole in the pole piece Q the armature A Will be rocked in a clockwise direction, as a result of which the magnetic pull P increases with the concurrent displacement of the armature nearly as a square function.

In Fig. 1a the force P is shown as a function of the displacement f of the armature. By increasing the displacement of the armature A and therefore of the attached member A the effective length of the spring F decreases, and this shortening can be as much as indicated by the dotted line position thereof in Fig. 1 wherein the effective length of the spring F is reduced to the extent that it is shorter than the piece A itself.

On the other hand, the spring F extends itself more and more in this direction of armature movement. The resultant force P from both springs is also shown in Fig. In as a function of the displacement f of the armature. By corresponding configuration of the springs F and F with suitable dimensioning it is possible without difficulty to achieve a spring characteristic such as shown by the broken-line curve P which is similar to the force-displacement curve P Owing to the fact that the spring forces and the magnetic driving forces work against each other, curves P P appear as reflected images of each other. The adjustment must be made in such a way that the magnetic driving force P is always a little greater than the spring force P in such manner that the resultant actuating force sk for a twoposition armature is configured as shown by the dotdash line. For a neutral-position armature, the force relations have to be reversed.

By energizing the relay coil W with direct current of reversed polarity, the pole piece Q is transformed to a north pole and correspondingly the pole piece Q to a south pole, and the armature is then displaced in counterclockwise dircction, the spring F now acquiring the greater tension and the spring F becoming increasingly relaxed.

I claim under priority of International Convention:

1. A relay comprising a pivoted armature; an elongated spring-backing member movable with said armature; a pair of spring fingers disposed on opposite sides 'tions away from each other and said backing member from said fixedend thereby biased to predetermined normal positions with substantial portions thereof out 'of contact with said backing member; and countcrbearing means-positioned opposite to, and each respectively engaged by, one of said free ends of the spring fingers, the latter acting-to dispose said armature in a predeterm-ined normal position with substantially minimum spring force acting thereon, pivotal displacement of said armature from said normal position causing one of said spring fingers to be flexed toward and against said backing member and the other thereof to flex away from the backing member, whereby to change the effective length and thereby the spring characteristic of the said fingers and the spring action thereof in predetermined desired relation to the amount of displacement of the armature; together with electromagnet means for displacing the armature.

2. A relay according to claim 1 and further characterized in that said counterbearing means is adjustable in a direction toward and away from each other and said free ends of the respective spring fingers to modify the biased condition of either of the latter relative to said backing member.

'3. A relay according to claim 1 in which said spring fingers have spring parameters including curvature,

length, and position in relation to the length and position of said backing member and positioning of said counterbearing means, all affording a progressive resultant spring characteristic which is self-adjusting as a function of the angular displacement of said armature.

'4. In a relay having an armature and electromagnetic means for attracting said armature according to a predetermined magnetic-foroe-displacement function, improvements comprising, to wit: spring means acting upon said armature to urge the same into a predetermined normal position from which the armature is displaced by energization of said electromagnetic means; said spring means including at least one spring member having attachment at one end to said armature and having another end engageable with a relative stationary counterbearing member, and means carried by said armature and engaged by said spring member responsive to displacement of the armature for changing the effective length, and spring action of said spring member according to a pattern having a predetermined relationship to the magnetic-force-displacement function aforesaid.

5. In an electromagnetic relay, a reversely rocking armature; electromagnet means for rocking said armature, a pair of elongated springs each fixed at the same end to move with said armature and having their remaining free end portions extending in the same direction away from the armature and the pivotal axis thereof in a direction normal to said axis, said free end portions of the springs being curved way from each other and respectively engaging a corresponding stationary bearing surface with a force acting in the non-energized condition of said electromagnet means to maintain said armature in a predetermined neutral rocking position,-said springs having a predetermined spring characteristic which changes by effective change in the length of said springs responsive to rocking movement of-the armatureand fiexure of the springs accordingly relative to the appertaining stationary bearing surface.

6. An electromagnetic relay of the spring-loaded armature type having spring means movable thereby with unattached end portions freely working against stationary means to change the effective spring length proportionately, in response to movement of the armature from a predetermined position, in such manner as to progressively change the force-characteristic of the spring means to approximately match the changing magnetic-forcetravel characteristic of the armature at least during the movement of the latter as the same is electromagnetically displaced from said predetermined position.

7. A relay according to claim 6 in which said spring means is a spring blade attached at one end to a pivoted armature to extend freely into space radially away from the pivotal axis, and having an arcuate portion near its free end portiongliding on a surface fixed in relation to said axis whereby to change the effective length of said spring conformably to the displacement of the armature as aforesaid.

8. A relay according to claim 7 in which said relay is polarized and said armature has a neutral position determined by two springs constructed and operating substantially as set forth but working oppositely in direction to each other to urge the armature into said neutral position.

References Cited in the file of this patent UNITED STATES PATENTS 2,190,685 Slater Feb. 20, 1940 2,294,484 Snavely et a1. Sept. 1, 1942 2,355,298 Horlacher Aug. 8, 1944 2,506,234 Neild May 2, 1950 2,767,279 Hall Oct. 16, 1956 FOREIGN PATENTS 410,690 Italy Apr. 20, 1945 

